Storage

University of Southern California (USC) is developing an iron-air rechargeable battery for large-scale energy storage that could help integrate renewable energy sources into the electric grid. Iron-air batteries have the potential to store large amounts of energy at low cost—iron is inexpensive and abundant, while oxygen is freely obtained from the air we breathe. However, current iron-air battery technologies have suffered from low efficiency and short life spans.

General Compression has developed a transformative, near-isothermal compressed air energy storage system (GCAES) that prevents air from heating up during compression and cooling down during expansion. When integrated with renewable generation, such as a wind farm, intermittent energy can be stored in compressed air in salt caverns or pressurized tanks. When electricity is needed, the process is reversed and the compressed air is expanded to produce electricity.

Proton Energy Systems is developing an energy storage device that converts water to hydrogen fuel when excess electricity is available, and then uses hydrogen to generate electricity when energy is needed. The system includes an electrolyzer, which generates and separates hydrogen and oxygen for storage, and a fuel cell which converts the hydrogen and oxygen back to electricity. Traditional systems use acidic membranes, and require expensive materials including platinum and titanium for key parts of the system.

Beacon Power is developing a flywheel energy storage system that costs substantially less than existing flywheel technologies. Flywheels store the energy created by turning an internal rotor at high speeds—slowing the rotor releases the energy back to the grid when needed. Beacon Power is redesigning the heart of the flywheel, eliminating the cumbersome hub and shaft typically found at its center. The improved design resembles a flying ring that relies on new magnetic bearings to levitate, freeing it to rotate faster and deliver 400% as much energy as today's flywheels.

General Atomics is developing a flow battery technology based on chemistry similar to that used in the traditional lead-acid battery found in nearly every car on the road today. Flow batteries store energy in chemicals that are held in tanks outside the battery. When the energy is needed, the chemicals are pumped through the battery. Using the same basic chemistry as a traditional battery but storing its energy outside of the cell allows for the use of very low-cost materials.

City University of New York (CUNY) Energy Institute is working to tame dendrite formation and to enhance the lifetime of Manganese in order to create a long-lasting, fully rechargeable battery for grid-scale energy storage. Traditional consumer-grade disposable batteries are made of Zinc and Manganese, two inexpensive, abundant, and non-toxic metals, but these disposable batteries can only be used once.

United Technologies Research Center (UTRC) is developing a flow battery with a unique design that provides significantly more power than today's flow battery systems. A flow battery is a cross between a traditional battery and a fuel cell. Flow batteries store their energy in external tanks instead of inside the cell itself. Flow batteries have traditionally been expensive because the battery cell stack, where the chemical reaction takes place, is costly. In this project, UTRC is developing a new stack design that achieves 10 times higher power than today's flow batteries.

Lawrence Berkeley National Laboratory (LBNL) is designing a flow battery for grid storage that relies on a hydrogen-bromine chemistry which could be more efficient, last longer, and cost less than today's lead-acid batteries. Flow batteries are fundamentally different from traditional lead-acid batteries because the chemical reactants that provide their energy are stored in external tanks instead of inside the battery. A flow battery can provide more energy because all that is required to increase its storage capacity is to increase the size of the external tanks.

The University of Tennessee, Knoxville team will develop an energy storage system based on an innovative electrolyzer/fuel cell combination. Typically, fuel cells produce water from hydrogen and oxygen. The Tennessee team will instead use the fuel cell to produce hydrogen peroxide, a liquid that can be stored. When extra power is needed on the grid, the fuel cell will produce peroxide and electricity. Available electricity then can be used to convert the peroxide back to hydrogen and oxygen during the charging cycle, which can be stored for future use.

The Echogen Power Systems team will develop an energy storage system that uses a carbon dioxide (CO2) heat pump cycle to convert electrical energy into thermal energy by heating a “reservoir” of low-cost materials such as sand or concrete. During the charging cycle, the reservoir will store the heat that will be converted into electricity on demand in the discharge or generating cycle. To generate power, liquid CO2 will be pumped to a supercritical pressure and brought to a higher temperature using the stored heat from the reservoir.